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80 Cards in this Set

  • Front
  • Back
4 layers of the walls of each organ that makes up GI tract:
1. Mucosa
2. Submucosa
3. Muscularis externa
4. Serosa (adventitia)
Where is the mucosa?
It borders the GI tract lumen
3 Subdivisions of the mucosa:
1. Epithelium
2. Lamina propria
3. Muscularis mucosa
What type of epithelium lines the esophagus and anal canal? Why?
Stratified squamous non-keratinized - to protect against abrasion.
What type of epithelium lines the stomach? Why?
Simple columnar - to secrete mucus to protect the stomach from acid.
What type of epithelium lines the small and large intestines? Why?
Simple columnar - for absorption and mucous secretion.
What is the lamina propria?
Loose connective tissue deep to the epithelium of the mucosa.
Functions of the lamina propria:
-Supports overlying epithelium
-Nourishes the epithelium
Cells within the lamina propria:
immune cells
What structure is present in small intestine lamina propria? Why?
Fenestrated blood capillaries and lymphatic caps to receive absorbed nutrients.
What is the function of muscularis mucosa?
To facilitate digestion and absorption by moving and folding the mucosa.
What is the submucosa?
A layer of loose connective tissue that contains larger blood vessels and lymphatics.
What plexus is housed in the submucosa?
Meissner's plexus
Muscularis Externa consists of:
-Inner circular smooth muscle
-Outer longitudinal smooth muscle
What is the muscularis externa made up of in the upper 1/3rd of the esophagus?
Skeletal muscle
Which plexus controls contractions of the muscularis externa?
The myenteric plexus
What type of epithelium is the Serosa?
Simple squamous
What is the serosa?
The visceral peritoneum covering GI tract organs.
Function of the serosa:
secretion of serous fluid to lubricate movements of the GI organs against one another.
What organs have an adventitia?
Those that are retroperitoneal or outside the peritoneal cavity.
What is the difference between an adventitia and a serosa?
The adventitia covers organs and blends with surrounding tissues; the serosa is on free organs within the peritoneal cavity.
The ENS is part of:
the ANS
How does the PNS interact with the ENS?
The Vagus nerve acts on the postganglionic neurons of the submucosal and myenteric plexuses to stimulate secretion and peristalsis.
How does the SNS affect the ENS?
-Inhibits peristalsis
-Stimulates sphincters
What does the esophagus do?
Propels a food bolus from the oropharynx to the stomach.
What does nonkeratinized mean?
What lines the esophagus?
Stratified Squamous Wet epithelium
What special cells are present within the surface epithelium of the esophagus?
Langerhans cells
Function of langerhan's cells:
What does the lamina propria of the esophagus contain?
2 clusters of cardiac glands
Where are these cardiac gland clusters located?
-Near the oropharynx
-Near the stomach
What do the cardiac glands produce?
Mucous that helps propel the food bolus
Where in the esophagus is the muscularis mucosa most prominent?
Near the stomach (less at the top)
3 subdivisions of the muscularis externa of the esophagus:
Top: skeletal
Mid: mixed
Bot: smooth
How do you know when you've reached the Gastro-esophageal Junction?
the wet stratified squamous epi transitions to Simple Columnar
What type of sphincters does the esophagus have?
What are the 2 physiological sphincters of the esophagus? Function of each?
-Pharyngoesophageal - prevents acid reflux
-Gastroesophageal - prevents food reflux
When are rugae visible?
When the stomach is empty
What happens to rugae when the stomach is full?
They flatten
What type of epithelium lines the stomach?
Simple cuboidal
What do we call those cells?
Surface mucous cells
What do the surface mucous cells secrete and how does it function?
A thick mucous
-Protects the underlying mucosa from the stomach's acid
What is the surface of the stomach like?
It has pits with gastric glands sitting at the base.
Where are the gastric glands located exactly?
In the stomach's lamina propria
What facilitates the digestive functions of the stomach?
The churning action of the muscularis externa
What are the 3 layers of the stomach's muscularis externa?
1. Inner oblique
2. Middle circular
3. Outer longitudinal
What 4 cell types compose the gastric glands?
1. Chief cells (Zymogenic)
2. Enteroendocrine cells
3. Stem cells
4. Parietal cells
What do chief cells secrete?
-Gastric lipase
Where are the nuclei of chief cells located?
At the basal side of the cell (away from the lumen)
What color are chief cells? Why?
Basophilic due to their abundant rER
What are Enteroendocrine cells?
Cells that secrete hormones into the lamina propria to influence the activity of nearby or distant cells.
Example of something the enteroendocrine cells secrete:
How are stem cells identifiable?
They'll be dividing
Where are stem cells commonly found within gastric pits?
Near the neck - upper region
What do these stem cells give rise to?
All other cell types in the stomach epithelium
How often does the gastric epithelium renew?
Completely every 3 days
How are parietal cells identifiable?
They are eosinophilic with centrally located nuclei
What do parietal cells secrete?
HCl and Gastric IF
What is unique about the cell membranes of parietal cells?
They are deeply invaginated forming intracellular canaliculi to increase their SA for secretion.
What is on the surface of the intracellular canaliculi of parietal cells?
What happens to the excess plasma membrane when Parietal cells are not actively secreting?
It gets stored as a tubulovesicular system deep to the cell surface.
What are the 3 stages of the stomach's response to food intake?
1. Cephalic phase
2. Gastric phase
3. Intestinal phase
What is the cephalic phase?
Anticipation of a meal in response to visual cues
What NT from the vagus/cephalic stim triggers the ENS to start gastric secretions?
What does that ACh trigger?
Gastrin secretion from neuroendocrine cells
What does gastrin in turn stimulate?
Acid secretion from parietal cells
What happens in the gastric phase?
Stomach distention further triggers acid secretion
What happens in the intestinal phase?
The transfer of chyme from stomach to duodenum slows down further emptying of the stomach.
What is this reflex called?
The gastric inhibitory reflex - Enterogastric reflex
What further suppresses gastric activity during the intestinal phase?
Secretion of CCK and Secretin from the small intestine.
4 types of stomach pathology:
-Hiatal hernia
-Gastroesophageal reflux disease
-Barrett's esophagus
-Peptic ulcers
What is the cause of hiatal hernias?
Displacement of the proximal stomach thru the diaphragm - loosening the physiologic gastroesophageal sphincter
What is GERD?
Just acid reflux from the stomach into the esophagus
What is GERD often percieved as?
Perisstent heartburn
What is Barrett's esophagus?
Persistant esophag reflux that leads to breakdown of the epithelial lining.
What is it when the wet stratified squamous epithelium of the esophagus transitions to a columnar phenotype?
Possibly precancerous
What are peptic ulcers?
Abrasians of the mucosa of the stomach or duodenum
What is the major cause of peptic ulcers?
H Pylori (sometimes NSAIDS)
What does not cuase peptic ulcers?
Spicy foods and stress
How does H. pylori work?
It uses urase to breakdown stomach acid and facilitate colonization.